Basic Spatiotemporal Gait Variables of Young and Older Healthy Volunteers Walking Along a Novel Figure-of-8 Path

Background: Locomotion along curved trajectories requires fine coordination among body segments. Elderly people may adopt a cautious attitude when steering. A simple, expeditious, patient-friendly walking protocol can be a tool to help clinicians. We evaluated the feasibility of a procedure based upon a newly designed Figure-of-eight (nFo8) path and an easy measurement operation.Methods: Sixty healthy volunteers, aged from 20 to 86 years, walked three times at self-selected speed along a 20 m linear (LIN) and the 20 m nFo8 path. Number of steps, mean speed and walk ratio (step length/cadence) were collected. Data were analysed for the entire cohort and for the groups aged 20–45, 46–65, and >65 years.Results: There was no difference in mean LIN walking speed between the two younger groups but the oldest was slower. During nFo8, all groups were slower (about 16%) than during LIN. Cadence was not different across groups but lower during nFo8 in each group. Step length was about 8% shorter in the two younger groups and 14% shorter in the oldest during nFo8 compared to LIN. Walk ratio was the smallest in the oldest group for both LIN and nFo8.Conclusions: A complex nFo8 walking path, with fast and easy measurement of a simple set of variables, detects significant differences with moderate and large effects in gait variables in people >65 years. This challenging trajectory is more revealing than LIN. Further studies are needed to develop a quick clinical tool for assessment of gait conditions or outcome of rehabilitative treatments.

Artificial gauge induced dispersionless coupling for broadband photonic waveguide integration

Coupling among waveguides plays an important role in photonic integration, while it usually suffers from large wavelength dispersion and structural sensitivity that brings difficulties in broadband and robust photonic chip devices. Here, we report a new strategy of dispersion engineering of coupled waveguides by artificial gauge field (AGF) with curved trajectories, which gives rise to a dispersionless broadband coupler function in high-density silicon waveguides (waveguide pitch <λ/2). It is found that the artificial gauge field can generate an inverse dispersion to compensate for the dispersion of conventional waveguide coupling. As such, the coupling between the waveguides can be stable in a broad bandwidth. Based on this design, we demonstrate compact directional and 3dB couplers that show broadband dispersionless coupling of light with wavelength from 1400 to 1650 nm, which also exhibit robustness to considerably large structural variations ~150 nm (75% structural deviation). Furthermore, using the AGF coupler as the building block, we significantly demonstrate a three-level-cascaded waveguide network to route the broadband light to the desired ports, showing a tremendous advantage over the conventional counterparts. Our work exploits the artificial gauge field to integrated photonics and demonstrates the possibility of massive, broadband, robust and dense photonic integrations.

Design of a Mechanism with Embedded Suspension to Reconfigure the Agri_q Locomotion Layout

The Agri_q is an electric unmanned ground vehicle specifically designed for precision agriculture applications. Since it is expected to traverse on unstructured terrain, especially uneven terrain, or to climb obstacles or slopes, an eight-wheeled locomotion layout, with each pair of wheels supported by a bogie, has been chosen. The wide contact surface between the vehicle and the ground ensures a convenient weight distribution; furthermore, the bogie acts like a filter with respect to ground irregularities, reducing the transmissibility of the oscillations. Nevertheless, this locomotion layout entails a substantial lateral slithering along curved trajectories, which results in an increase of the needed driving torque. Therefore, reducing the number of ground contact points to compare the torque adsorption in different configurations, namely four, six, or eight wheels, could be of interest. This paper presents a reconfiguration mechanism able to modify the Agri_q locomotion layout by lifting one of the two wheels carried by the bogie and to activate, at the same time, a suspension device. The kinematic synthesis of the mechanism and the dynamic characteristics of the Agri_q suspended front module are presented.

Does Curved Walking Sharpen the Assessment of Gait Disorders? An Instrumented Approach Based on Wearable Inertial Sensors

Gait and balance assessment in the clinical context mainly focuses on straight walking. Despite that curved trajectories and turning are commonly faced in our everyday life and represent a challenge for people with gait disorders. The adoption of curvilinear trajectories in the rehabilitation practice could have important implications for the definition of protocols tailored on individual’s needs. The aim of this study was to contribute toward the quantitative characterization of straight versus curved walking using an ecological approach and focusing on healthy and neurological populations. Twenty healthy adults (control group (CG)) and 20 patients with Traumatic Brain Injury (TBI) (9 severe, sTBI-S, and 11 very severe, sTBI-VS) performed a 10 m and a Figure-of-8 Walk Test while wearing four inertial sensors that were located on both tibiae, sternum and pelvis. Spatiotemporal and gait quality indices that were related to locomotion stability, symmetry, and smoothness were obtained. The results show that spatiotemporal, stability, and symmetry-related gait patterns are challenged by curved walking both in healthy subjects and sTBI-S, whereas no difference was displayed for sTBI-VS. The use of straight walking alone to assess gait disorders is thus discouraged, particularly in patients with good walking abilities, in favor of the adoption of complementary tests that were also based on curved paths.

Spherical Universe: History of the Universe Assuming a Closed Spherical Shape

This theory assumes the universe it is a closed sphere inside a “shell” which holds it still preventing it from expanding or collapsing. Before big bang, the universe must have been filled with linear radiation and no mass, space was flat and time was zero (empty set). An initial big bang took place everywhere inside the shell having as purpose to curve flat space and to create mass and time. At initial moment mass got created along with all existing physical laws. Later on, stars and planets formed by gathering of mass, and then accumulated into galaxies which move randomly by curved trajectories. Inside the universe there are no lines and even light travels on long distances by curved trajectory. It cannot be an expansion of the universe since the “shell” doesn’t allow that to happen. Behaviour of curved space at subatomic level generated by the initial big bang is still happening today and this prevents all spheres of mass inside the universe from stop moving. Light coming from far distance galaxies is being curved by the behaviour of space at subatomic level at a constant linear rate with distance and time. If more time and space is given to a star, light reaching us it will shift to red even more, do to a much more curved trajectory. The universe is fixed with a constant diameter, space itself doesn’t move in any linear direction, it just curves onto itself

Energy estimation for differential drive mobile robots on straight and rotational trajectories

Energy autonomy is an important aspect that needs to be improved in order to increase efficiency in mobile robotic tasks. Having accurate power models allows the estimation of energy consumption along different trajectories. This article proposes a power model for two-wheel differential drive mobile robots. The proposed model takes into account the dynamic parameters of the robot and its motors, and predicts the energy consumption for trajectories with variable accelerations and variable payloads. The experimental validation of the proposed model was performed with a Nomad Super Scout II mobile robot which was driven along straight and curved trajectories, with different payloads and accelerations. The experiments using the proposed model showed accuracies of 96.67% along straight trajectories and 81.25% along curved trajectories in the estimation of energy consumption.

Determination of the Trajectory of Curvilinear Motion of Front Steering Wheels Driven Tractor

The issue of designing the machine tractor movement trajectory is relevant today because its optimization significantly reduces fuel consumption and thus the transport costs. Proper choice of the energy machine and agricultural machinery with economy consumption of fuel and lubricants is also crucial. Recently, the problem has received scant attention in scientific literature. Therefore, this study analytically determines the trajectory of turning the tractor with front steering wheels and attempts to describe the curvilinear trajectory of a four-wheeled tractor using parametric equations in Cartesian coordinates. Its outcomes have a number of important implications for future practice; they are applicable e.g. in planning curved trajectories when cornering the tractor during field processing or in fuel and time consumption predictions for certain operations.